RUTLAND — Lawyers representing convicted killer Frank Caraballo argued Wednesday that contradictory verdicts handed down by a jury in October should lead a federal judge to acquit him on one of the convictions.

Caraballo, 31, was convicted at the end of October of conspiracy to distribute heroin, cocaine and crack cocaine, use of a firearm while drug trafficking, and causing the death “by murder through the use of a firearm” of Melissa Barratt. The body of Barratt, 30, of Brattleboro, was found July 29, 2011, in the woods of Dummerston.

He faces a potential life sentence on each of those charges.

But while jurors found Caraballo guilty of causing Barratt’s death, they found him not guilty of pulling the trigger on the gun that killed her.

During arguments in U.S. District Court in Rutland this week, Caraballo’s defense team argued that the conviction for causing Barratt’s death should be overturned because the government’s case rested on the principle that Caraballo was the shooter.

“It’s a core piece of the government’s case,” defense attorney Natasha Sen said Wednesday. “There are insufficient facts to support causation.”

Only one witness, Joshua Makhanda-Lopez, who was Caraballo’s partner in distributing drugs in southern Vermont, testified that he saw Caraballo execute Barratt by standing behind her and shooting her once in the back of the head.

Judge Christina Reiss said it was possible that jurors didn’t know if Caraballo pulled the trigger himself but believed that he caused her death by instructing someone else to do the killing.

But Sen said if that was what jurors believed, then they reached a verdict that was supported by no evidence or testimony in the trial.

“There’s no evidence he caused anyone to do anything,” she said.

“The blame throughout the trial was placed squarely on Mr. Caraballo. There’s no evidence at all that he ever directed anyone else to harm Ms. Barratt.”

Assistant U.S. Attorney Paul Van de Graaf argued it was futile to guess at the reasons why jurors reached their decision. What mattered, he said, was whether the evidence in the case was sufficient for a jury to find Caraballo guilty of causing Barratt’s death.

“There are all kinds of reasons why jurors reach their decisions, and the high court has said it’s not the court’s job to interpret their decisions,” Van de Graaf said. “I think there’s more than sufficient evidence that he did pull the trigger and the evidence is powerful in this case that these two men went into the woods with Ms. Barratt.”

During Caraballo’s trial, his defense team argued that Makhanda-Lopez killed Barratt. During arguments in court last week, Sen said the jury’s verdict gave credence to the theory that Makhanda-Lopez acted on his own.

But the judge said that scenario seemed unlikely since Caraballo was the one in charge.

“It seems that Mr. Lopez made very few decisions on his own, and it was not his drugs that were stolen,” Reiss said, referring to the motive that prosecutors say Caraballo had for killing Barratt.

The judge didn’t make a decision on the acquittal Wednesday, instead taking the matter under advisement.